1. Field of the Invention
The present invention relates to a laminated heat exchanger constructed by laminating tube elements alternately with fins. The laminated heat exchanger is used for air conditioning systems for vehicles, residential facilities and the like.
2. Description of the Related Art
Laminated heat exchangers in the known art include those formed by laminating tube elements, each of which is provided with tank portions and a passage communicating with the tank portions over a plurality of levels. Fins are provided between the tube elements, and adjacent tube elements are bonded at the tank portions so that they communicate in the direction of the lamination. End plates are provided on the outside of the tube elements at the ends of the assembly.
In such a laminated heat exchanger, the tube elements at the ends may each be formed by bonding a formed plate, provided with distended portions for tank formation and a distended portion for passage formation, to a flat formed plate. However, if a flat formed plate is employed, there is a problem in that the passage cross section will be small, and in order to prevent this, it is desirable to have indentations and projections on the surface of the flat plate which correspond to those on the surface of the formed plate to which it is to be bonded face-to-face. In other words, it is desirable to form distended portions in the flat formed plate where such plate faces opposite the distended portions for tank formation and the distended portion for passage formation of the formed plate to which the flat formed plate is to be bonded face-to-face. It is also desirable to form beads and the like on the flat formed plate, similar to those formed in the distended portion for passage formation.
However, as shown in FIG. 8, even if an end plate B is mounted to a flat formed plate A, provided with indentations and projections on the surface formed with beads or the like, it does not necessarily mean that complete surface-to-surface bonding can be achieved. Also, if the end plate is placed in contact so as to block some of the indented portions C, it will result in a reduction of bonding surface area. Also, unless the end plate B and the flat formed plate A are bonded over a specific area, they may become deformed during assembly with the use of jigs or in the finished product due to insufficient bonding strength. Furthermore, if a gap is formed between any of the indented portions C and the end plate B, water D may collect in the gap, and this water D will freeze and expand repeatedly, resulting in cracking of the flat formed plate A and thereby creating a coolant leak.